This invention relates to insulating oil compositions used in oil-filled or oil-immersed electrical devices.
Insulating oil is widely used in various types of electrical devices such as power cables, transformers, capacitors and so on. It has hithereto been customary to use mineral oil or diphenyl chloride as the insulating oil for such electrical devices. Recently, such electrical devices tend to become of greater capacity and more capable of withstanding higher voltages, so that the insulating oil used in them must have characteristics to meet the tendncy.
Mineral oil alone, however, is combustible and inferior in such electrical characteristics as dielectric constant and visible gas generating voltage. While diphenyl chloride is incombustible and superior in the above-mentioned characteristics, it is very toxic to the human body so that the use of this compound is undesirable from the view point of environmental pollution.
Accordingly, the primary object of the invention is to provide an insulating oil composition which has good characteristics as such oil.
Another object of the invention is to provide an insulating oil composition which is superior to mineral oil in electrical characteristics such as dielectric constant, visible gas generating voltage, etc.
Another object of the invention is to provide such an insulating oil composition as aforesaid which is incumbustible and has no toxicity to the human as well as animal life.
In accordance with the invention there is provided an insulating oil composition which comprises a mixture of trixylenylphosphate (which will be referred to as TXP) and an insulating oil having a viscosity of 5 to 15 centipoises (which will be abbreviated to cp) at 30.degree.C, the amount of of the latter oil to be mixed with TXP being 10% to 40% by volume of the mixture. The insulating oil which has a viscosity of 5 cp to 15 cp can be selected from the following group: mineral oil (to be referred to as MO), alkylbenzene (to be referred to as AB), alkylnaphthalene (to be referred to as AN), diallylalkane (to be referred to as DAA), paraffin hydrocarbon oil (to be referred to as PO), naphthene hydrocarbon oil (to be referred to as NO), 2-diphenylmethylether (to be referred to as DME), 2-diphenylisopropylether (to be referred to as DPE), etc.